A μ-PCD method has been known as a method for measuring the effective carrier lifetime of photoinduced carriers (minority carriers) generated in a semiconductor substrate (see J. M. Borrego, R. J. Gutmann, N. Jensen, and O. Paz: Solid-Sate Electron., 30, 195 (1987), for example). The μ-PCD method applies an ultrashort light pulse to the semiconductor substrate in a state in which microwaves are applied to the semiconductor substrate. The microwaves are reflected by carriers induced by the light pulse, and a temporal change in reflection intensity is measured to determine the effective carrier lifetime of the photoinduced carriers.
A QSSPC method has also been known as a method for measuring the effective carrier lifetime of photoinduced carriers generated in a semiconductor substrate (see G. S. Kousik, Z. G. Ling, and P. K. Ajmera: J. Appl. Phys., 72, 141 (1992), for example). According to the QSSPC method, an inductance coil is disposed to face the semiconductor substrate, and radio frequency (RF) electromagnetic waves are applied to the semiconductor substrate. An ultrashort light pulse is also applied to the semiconductor substrate. The RF electromagnetic waves are reflected by carriers induced by the light pulse, and a temporal change in reflected waves is measured as a change in current that flows through the coil to determine the effective carrier lifetime of the photoinduced carriers.
A microwave optical interference absorption method has also been known as a method for measuring the effective carrier lifetime of photoinduced carriers generated in a semiconductor substrate (see T. SAMESHIMA, H. HAYASAKA, and T. HABA: Jpn. J. Appl. Phys. 48 (2009) 021204-1-6, for example). According to the microwave optical interference absorption method, the semiconductor substrate is inserted into a microwave interferometer that is formed using a waveguide, and continuous light is applied to the semiconductor substrate in a state in which microwaves are applied to the semiconductor substrate. The microwaves are absorbed by carriers induced by the continuous light, and a decrease in microwave transmittance is measured to determine the effective carrier lifetime of the photoinduced carriers.
A method has been known that applies periodic intermittent pulsed light to the semiconductor substrate when implementing the method described in (see Toshiyuki Sameshima, Tomokazu Nagao, Shinya Yoshidomi, Kazuya Kogure, and Masahiko Hasumi: “Minority Carrier Lifetime Measurements by Photo-Induced Carrier Microwave Absorption Method”, Jpn. J. Appl. Phys. 50 (2011) 03CA02, and WO11/099,191, for example). According to this method, the effective carrier lifetime can be calculated regardless of the intensity of irradiation light by changing the irradiation time and the cycle of the pulsed light.